Passive recirculation device

ABSTRACT

The present disclosure provides a recirculation device comprising a body comprising at least one first passage configured to receive an exhaust, at least one second passage configured to receive a fuel, at least one third passage configured to receive a mixture of the exhaust and the fuel, and a longitudinal axis extending from the second passage to the third passage. The device can also comprise a nozzle comprising an inner cavity for directing fuel towards an orifice, located at the smallest cross-sectional area of the inner cavity and a piston slideably located within the body comprising a first end configured to receive the fuel and a second end configured to fuel to the nozzle cavity, whereby the piston can be actuated along the longitudinal axis of the body by the exhaust controlling the flow of fuel passing through the orifice. A mixing chamber located within the body can be configured to receive an exhaust and configured to receive fuel from the orifice.

RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.13/956,477, filed Aug. 1, 2013, which claims the benefit of U.S.Provisional Application No. 61/680,845, filed Aug. 8, 2012, the entirecontents of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a recirculation device for passivelycontrolling fluid flow. In some embodiments, the recirculation devicedescribed herein can be used to control an amount of fuel supplied to arecirculation loop of a fuel cell.

BACKGROUND

Various devices, such as valves or ejectors, are used to control fluidflow in liquid and gas form. Such devices are often incorporated into amechanical assembly in order to control the flow of a fluid within theassembly or flows of fluid into or out of the assembly. To increase ordecrease such fluid flow, valves or ejectors can have integratedelectrical, pneumatic, or mechanical control components. While theseactive control mechanisms are commonly used, passive control based onthe fluid pressure is less common because of difficulties accuratelycontrolling fluid flow or sizing components to ensure effectiveoperation over a wide range of conditions.

A fuel cell is a device for generating electric power. The chemicalenergy from a fuel is converted into electricity through a chemicalreaction with oxygen or other oxidizing agent. The chemical reactiontypically yields electricity, heat, and water. In operation, fuel cellsusually require controlled flows of fuel, oxidizing agent, or coolingfluid.

A fuel cell can include an anode in an anode compartment, a cathode in acathode compartment, and an electrolyte that allows charges to movebetween the anode and cathode. Electrons are drawn from the anode to thecathode through an electric load circuit, producing electricity. To varyelectrical output, valves, ejectors, or other flow devices can beconfigured to control fluid flows to one or more compartments.

In some examples, a flow of fuel is supplied to an anode compartment,and a flow of oxygen containing gas (e.g., air) is fed to a cathodecompartment. The fuel can flow continuously through the anodecompartment while a portion of the fuel undergoes an electrochemicalreaction in the anode compartment, as represented by the equation below.

2H²→4H⁺+4e ⁻

Electrons produced by the anode electrochemical reaction are drawn fromthe anode to the cathode through an electric load circuit, producingdirect-current electricity. The positively charged ions produced by thereaction are drawn from the anode through the electrolyte to thecathode. An electrolyte can be configured to prevent the passage ofnegatively charged electrons while allowing the passage of positivelycharged ions.

Following passage of the positively charged ions through theelectrolyte, the ions can combine in the cathode compartment withelectrons that have passed through the electric load circuit. Thecombination can form a cathode electrochemical reaction in which wateris produced from the reduction of oxygen, as represented by the equationbelow.

O₂+4H⁺+4e ⁻→2H₂O

The amount of fuel oxidized in the anode compartment can be dependent onthe amount of power required from the electric load circuit. Not allfuel supplied to the anode compartment is oxidized as a portion of thefuel is discharged from the anode compartment.

To increase the overall efficiency of the fuel cell, the outlet from theanode compartment can flow back to the inlet of the anode compartment byway of a recirculation loop. To enable the fuel cell to continuouslyoutput power, fuel must be introduced into the recirculation loop toreplace the fuel that was oxidized in the anode compartment. The rate atwhich fuel is introduced into the recirculation loop will depend on theload being applied to the electrical circuit; the greater the load, themore fuel is required.

A flow of fuel introduced into the recirculation loop can be controlledby a variety of devices, including valves or ejectors. Supplying anappropriate amount of fuel to the recirculation loop when a fuel cellramps up from minimum to maximum power output, and vice versa, mayrequire multiple ejectors of varying sizes or a control valve capable ofthrottling the flow. Multiple ejectors with different size nozzles, aswell as control valves, can be costly and can increase a device'scomplexity.

Some prior art devices have reduced the need for multiple ejectors byusing variable flow ejectors, while others have used a control valve incombination with an ejector. For example, U.S. Pat. No. 6,858,340discloses a variable flow ejector for use in a fuel cell system. Twodiaphragms within the ejector control needle movement relative to thenozzle to regulate fluid flow through the ejector. U.S. Pat. No.7,536,864 and U.S. Pat. No. 6,779,360 use an actuator to control thenozzle opening. And U.S. Patent Application No. 2010/0068579 discloses acontrol valve used in conjunction with an ejector.

However, none of these valves and ejectors operate with passive controlbecause they all require some form of active control system. Forexample, multiple fluids are used to deform multiple diaphragms, amanaged actuator maneuvers a ram, a control actuator positions a needle,or a control valve throttles the flow based on downstream feedback. Thepresent disclosure overcomes at least some deficiencies of the priorart.

In consideration of the aforementioned circumstances, the presentdisclosure provides a recirculation device that can be integrated into afuel cell system. The recirculation device can passively control anoderecirculation flow based on anode compartment exhaust pressure. Thedevice may supply fuel to the fuel cell to permit operate over a rangeof conditions from a minimum to a maximum power output.

SUMMARY

One aspect of the present disclosure is directed to a recirculationdevice that can comprise a body comprising at least one first passageconfigured to receive an exhaust, at least one second passage configuredto receive a fuel, at least one third passage configured to receive amixture of the exhaust and the fuel, and a longitudinal axis extendingfrom the second passage to the third passage. The device can alsocomprise a nozzle comprising an inner cavity for directing fuel towardsan orifice, located at the smallest cross-sectional area of the innercavity and a piston slideably located within the body comprising a firstend configured to receive the fuel and a second end configured to fuelto the nozzle cavity, whereby the piston can be actuated along thelongitudinal axis of the body by the exhaust controlling the flow offuel passing through the orifice. A mixing chamber located within thebody can be configured to receive an exhaust and configured to receivefuel from the orifice.

Another aspect of the present disclosure is directed to a recirculationdevice, comprising a body comprising at least one first passageconfigured to receive an exhaust, at least one second passage comprisesa valve seat configured to receive a fuel, at least one third passageconfigured to receive a mixture of the exhaust and the fuel, and alongitudinal axis extending from the second passage to the thirdpassage. A nozzle comprising an inner cavity can direct fuel towards aorifice, located at the smallest cross-sectional area of the innercavity, wherein nozzle can be fixedly coupled to body. The recirculationdevice can also comprise a piston slideably located within the bodycomprising a first end configured to receive the fuel and a second endconfigured to fuel to the nozzle cavity, the piston surface can beconfigured to receive exhaust whereby the piston can be actuated alongthe longitudinal axis of the body by the exhaust controlling the flow offuel passing through the orifice. A mixing chamber can be located withinthe body configured to receive an exhaust and configured to receive fuelfrom the orifice and a valve stem comprising a tapered end can befixedly coupled to the first end of the piston, whereby the actuatedpiston along the longitudinal axis controls the distance between thevalve stem first end and valve seat.

Another aspect of the present disclosure is directed to recirculationdevice, comprising a body comprising at least one first passageconfigured to receive an exhaust, at least one second passage configuredto receive a fuel, at least one third passage configured to receive amixture of the exhaust and the fuel, and a longitudinal axis extendingfrom the second passage to the third passage. The device can alsocomprise a nozzle comprising an inner cavity for directing fuel towardsan orifice, located at the smallest cross-sectional area of the nozzlecavity, whereby nozzle can be fixedly coupled to the second end of thepiston. The device can also comprise a piston slideably located withinthe body comprising a central cavity configured to receive a firstneedle section through the full length of the piston central cavity,piston surface can be configured to receive exhaust, whereby the pistoncan be actuated along the longitudinal axis of the body by the exhaustpressure controlling the flow of fuel passing through the orifice. Amixing chamber can be located within the body configured to receive anexhaust and configured to receive fuel from the orifice. The device canalso comprise a needle fixedly coupled to the body comprising a firstsection comprising a passage for receiving the fuel which feeds into acentral cavity that connects to a second needle section whereby thefirst needle section and second needle section are fixedly coupled. Theneedle can also comprise a second section having an outlet passageallowing fuel to exit from the central cavity into the nozzle cavity;second needle section tapers toward the second end whereby the surfaceof the tapered needle section is parallel to the tapered inner surfaceof the nozzle and configured to engage the inner surface of the nozzleas the nozzle and piston actuate.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the disclosure, as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate several embodiments of thepresent disclosure and together with the description, serve to explainthe principles of the disclosure.

FIG. 1 is a schematic diagram of a fuel cell system, according to anexemplary embodiment.

FIG. 2A is a cut-away cross-sectional view of an ejector, according toan exemplary embodiment including an enlarged section of the ejector.

FIG. 2B is a schematic isometric view of a piston and valve stem,according to an exemplary embodiment.

FIG. 3A is a cut-away cross-sectional view of an ejector, according toanother exemplary embodiment.

FIG. 3B is a cut-away cross-sectional view of an ejector, according toanother exemplary embodiment.

DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to the present exemplaryembodiments of the disclosure, examples of which are illustrated in theaccompanying drawings. Wherever possible, the same reference numberswill be used throughout the drawings to refer to the same or like parts.

FIG. 1. is a schematic diagram of a fuel cell system 100, according toan exemplary embodiment. Fuel cell system 100 can comprise arecirculation device 110. For example, recirculation device 110 cancomprise a passive recirculation ejector as described below in detail.In addition to recirculation device 110, fuel cell system 100 cancomprise a fuel 120 and a fuel cell 120. Fuel 120 can comprise hydrogen,carbon monoxide, methanol, and dilute light hydrocarbons like methane.As explained above, fuel cell 130 can be configured to generateelectricity via a chemical reaction.

As shown in FIG. 1, fuel cell 120 can comprise an anode compartment 140,an anode 150, an electrolyte 160, a cathode compartment 170, a cathode180, and an electric load circuit 190. Electrolyte 160 can comprise apolymer membrane and an aqueous alkaline solution. In some embodiments,fuel cell 120 can comprise a proton exchange membrane, phosphoric acid,solid oxide, or molten carbonate.

A continuous flow of a mixed fuel 200 can be supplied to anodecompartment 140. A flow of oxygen 210 can be supplied to cathodecompartment 170. Once mixed fuel 210 enters anode compartment 140, aportion of the mixed fuel 200 may undergo an anode electrochemicalreaction at anode 150.

Not all mixed fuel 200 supplied to anode compartment 140 is necessarilyconsumed in an anode electrochemical reaction. A portion of mixed fuel200 that flows into anode compartment 140 may be discharged from anodecompartment 140 as an exhaust 220 through an anode compartment outlet230. Exhaust 220 discharged from anode compartment outlet 230 can exitat a lower pressure than mixed fuel 200 entering anode compartment inlet240 due to the fixed volume pressure reduction from the fuel consumed inthe anode electrochemical reaction.

Anode compartment outlet 230 may be fluidly connected to a first passage250 of recirculation device 110. Exhaust 220 can enter recirculationdevice 110 via first passage 250 and can be mixed with a flow of fuel120. Fuel 120 can be supplied through a second passage 260 ofrecirculation device 110. After exhaust 220 and fuel 120 are mixed inrecirculation device 110, the mixture can be discharged through a thirdpassage 270 as mixed fuel 200. Third passage 270 may be fluidlyconnected to anode compartment inlet 240, allowing mixed fuel 200 toflow into anode compartment 140. A flow of a recirculation loop 160 canflow between recirculation device 110 and fuel cell 130 as illustratedin FIG. 1.

Under typical operating conditions a pressure of fuel 120 at secondpassage 260 can range between about 30 to about 500 psig. A pressure ofexhaust 220 in first passage 250 can range between about three to about60 psig. And a pressure of mixed fuel 200 exiting third passage 270 canrange between about three to about 20 psig. The reasons for thesevariable pressure ranges are described below.

The anode electrochemical reaction taking place in anode compartment 140consumes mixed fuel 200 and reduces the fixed volume pressure within therecirculation loop 160. To counter this, recirculation device 110 may beoperated with continuous fuel recirculation. Specifically, fuel 120introduced into second passage 260 at a particular flow rate maymaintain the fixed volume pressure within the recirculation loop 160required to maintain power production from fuel cell 130 while electricload circuit 190 ramps up or down in power output. Recirculation device110 can be configured to regulate flow of fuel 120 as described above,i.e., passively and without active control.

FIG. 2A. is a cross-sectional diagram of recirculation device 110,according to an exemplary embodiment. Recirculation device 110 maycomprise a body 400, a nozzle 410, and a piston 420. As previouslydescribed, recirculation device 110 can be configured to receive exhaust220 via first passage 250 and fuel 120 via second passage 260. Flows offuel 120 and exhaust 220 can combine and mixed fuel 200 can exitrecirculation device 110 via third passage 270.

Body 400 can comprise a structure with an internal cavity 430 configuredto house nozzle 410 and piston 420. For example, body 400 may beconstructed of a metal, metal alloy, plastic, composite material, orequivalent material. Body 400 can have a coating or undergo surfacetreatments to reduce friction or increase corrosion protection. Forexample, a teflon coating or hard anodize treatment can be utilized.

Body 400 can comprise a single structure or an assembly of multiplepieces. In particular, recirculation device 110 can be designed for easyremoval from the fuel cell system 100 to allow for servicing orreplacement. For example, body 400 can comprise a first body section 440and a second body section 450. Body sections 440 and 450 may be fixedlyor removably coupled to each other using various attachment mechanisms.

Recirculation device 110 can include a longitudinal axis 460 extendingfrom an upstream section of body 400 to a downstream section of body400. For example, first body section 440 can be downstream (i.e., theright side in FIG. 2A) and second body section 450 can be placedupstream (i.e., the left side in FIG. 2A). Fuel 120 can flow generallyparallel to longitudinal axis 460 from upstream to downstream. Exhaust220 can flow generally perpendicular to longitudinal axis 460 and fuel120, and can be mixed with fuel 120 to form mixed fuel 200 that may alsoflow generally parallel to longitudinal axis 460 from third passage 270.

Third passage 270 can extend through at least part of body 400 or firstbody section 440. For example, third passage 270 can extend from aninner surface of internal cavity 430 to an exterior surface of firstbody section 440. Third passage 270 can include a tapered section andmay be configured to enhance mixing of fuel 120 and exhaust 220.

First passage 250 can be configured to receive exhaust 220. Althoughfirst passage 250 is shown as perpendicular to third passage 270 in FIG.2A, first passage 250 can be oriented at various angles relative tothird passage 270. First passage 250 may extend through at least part ofbody 400 or first body section 440. In particular, first passage 250 mayextend from an outer surface of body 400/first body section 440 to aninner surface of internal cavity 430. Other embodiments, first passage250 may comprise multiple passages configured to receive exhaust 220.

Second passage 260 can be configured to receive a flow of fuel 120. Insome aspects, second passage 260 can extend from an exterior surface ofbody 400 or second body section 450 to an inner surface of internalcavity 430. Second passage 260 can include various couplings (not shown)configured to couple to a fuel 130 supply line.

Connection fittings (not shown) at first passage 250, second passage260, third passage 270, anode compartment inlet 240, or anodecompartment outlet 230 may utilize a quick-connect coupling orequivalent style connections to allow for easy assembly or disassembly.The connection fittings may be configured to absorb vibration orpressure fluctuations that can be caused by discharged of flow from thenozzle 410.

In an alternate embodiment (not shown), the geometry of recirculationdevice 110 may be integrated into a portion of fuel cell 130. Such aconfiguration may eliminate the need for interconnecting fittings.

Body 400 can be configured to receive nozzle 410. Nozzle 410 can beconfigured to introduce a flow of fuel 120 into a mixing chamber 470where fuel 120 is combined with exhaust 220. Mixed fuel 200 issubsequently output from recirculation device 110 and forms part ofrecirculation loop 280.

Nozzle 410 can be configured to accelerate a flow of fuel 120 as itflows from an upstream location (to the left as shown in FIG. 2A) to adownstream location (to the right as shown in FIG. 2A). Nozzle 410 canbe shaped or sized to aerosolize fuel 120 to permit sufficient mixing offuel 120 with exhaust 220 in mixing chamber 470. Nozzle 410 can beconfigured so the flow rate of fuel discharged from nozzle 410 creates arelative negative pressure in the mixing chamber 470 region lateral tothe nozzle.

In some embodiments, nozzle 410 can be configured to operate withsupersonic fluid flow. Nozzle 410 may also be configured to receive aflow of exhaust 220 generally perpendicular to a flow of fuel 120exiting nozzle 410. An outer surface of nozzle 410 may be configured toform a substantially turbulent flow of exhaust 220 about the flow offuel 120 exiting nozzle 410. In particular, a flow of exhaust 220 mayswirl around nozzle 410 in a generally circular motion about a jet offuel 120 exiting nozzle 410. Such different flow paths of fuel 120 andexhaust 220 may enhance mixing of the two flows of fluids.

Nozzle 410 may be constructed of a metal, metal alloy, compositematerial or equivalent material able to handle high pressure and highvelocity fluid applications without eroding. The inner surface of nozzle410 can have a polished low friction finish to maximum flow-rateefficiency or maintain high discharge velocity of fuel 120.

In other embodiments, nozzle 410 can be formed as part of the body 400,creating a single structure of body 400 and nozzle 410. And in yet otherembodiments, nozzle 410 can be formed as part of first body section 440or second body section 450.

Nozzle 410 can divide internal cavity 430 into a mixing chamber 470downstream of nozzle 410 and a piston chamber 480 upstream of nozzle410. Mixing chamber 470 and piston chamber 480 may be fluidly connected.For example, exhaust 220 could flow from first passage 250 or mixingchamber 470 to piston chamber 480. For example, one or more throughports 490 can be configured to permit fluid flow into piston chamber 480from mixing chamber 470.

In other embodiments, the flow of exhaust 220 into piston chamber 480can be by way of a passage in the body 400 structure which fluidlyconnects the mixing chamber 470 to the piston chamber 480.

Nozzle 410 can have a first end 500 located generally upstream and asecond end 510 located generally downstream. Nozzle 410 can comprise anozzle cavity 520 located between first end 500 and second end 510,wherein nozzle cavity 520 may be configured to provide passage of fuel120 through nozzle 410. As shown in FIG. 2A, nozzle cavity 520 candecrease in diameter, narrowing while extending from first end 500 tosecond end 510.

Second end 510 can comprise an orifice 620 configured to permit a flowof fuel 120 to pass from nozzle cavity 520 to mixing chamber 470.Orifice 620 can be shaped to provide spray or flow distribution of fuel120 into mixing chamber 470. Orifice 620 could be located at an end-mostsurface of second end 510 or located generally within a downstreamregion of second end 510. It is also contemplated that orifice 620opening may comprise a cross-sectional shape of a square, rectangle,circle, triangle, or other shape.

First end 500 of nozzle 410 can be configured to receive fuel 120 intonozzle cavity 520. In particular, first end 500 can receive at leastpart of piston 420. In other embodiments, nozzle 410 may not receivepiston 420. Rather piston 420 may be received by a portion of body 400which fluidly connects to nozzle cavity 520.

Piston 420 can be configured to provide passage of fuel 120 from secondpassage 260 to first end 500 of nozzle 410. Piston 420 can also beconfigured to control flow of fuel 120 passing through second passage260 to first end 500 of nozzle 410 and out of orifice 620. In someembodiments piston 420 can control flow of fuel 120 based on a pressureof exhaust 220 formed in piston chamber 480.

Piston 420 may be constructed of a metal, metal alloy, compositematerial or equivalent material able to handle high pressure and highvelocity fluid applications.

Piston 420 may be slideably located in piston chamber 480 formed withinfirst body section 440. In other embodiments, piston 420 may beslideably located in piston chamber 480 formed within second bodysection 450 or single body 400 comprising a single structure.

Piston 420 may slide along piston chamber 480 inner surface by way of abearing or equivalent mechanism while still maintaining a sealed edge.The outer edge of piston 420 can be configured to seal tight against thepiston chamber 480 inner surface in order to prevent exhaust 220 frombypassing piston 420.

In an alternate embodiment, a diaphragm (not shown) can be used to allowsliding of piston 420 in relation to piston chamber 480. A diaphragmseal (not shown) may be fixed to the outer wall of piston 420 and innerwall of piston chamber 480.

Adequate friction between piston 420 and piston chamber 480 surface maybe present to prevent rapid oscillation of the piston 420 in response toexhaust 220 pressure fluctuations. Piston chamber 480 can be generallycylindrical configured to receive piston 420. In other embodiments,piston chamber 480 may be a different shape. For example, piston chamber480 maybe a square, oval, or rectangle configured to receive a piston420 having a corresponding shape.

Piston 420 can have a first end 540 being the upstream end and a secondend 550 being the downstream end. Piston 420 can have a piston cavity560 located between first end 540 and second end 550 providing fluidpassage from a region about first end 540 to second end 550. Second end550 can fluidly connect with nozzle cavity 520.

Piston 420 can comprise a piston head 530. Piston head 530 can extendlaterally from a wall surrounding piston cavity 560 toward pistonchamber 480 inner surface. Piston head 530 can generally move alonglongitudinal axis 460 in piston chamber 480. Piston head 530 can beconfigured to a flow of exhaust 220 at a piston head surface 570. Inparticular, a pressure of exhaust 220 can be exerted against piston headsurface 570 to move piston 420 longitudinally.

First end 540 of piston 420 can comprise a valve stem 590. Valve stem590 can have a tapered end configured to mate with a valve seat 600. Aninlet passage 610 can be located in the general region of first end 540.Inlet passage 610 can allow fuel 120 that flows from second passage 260and passes between valve seat 600 and valve stem 590 to flow into pistoncavity 560.

As discussed above, recirculation device 110 can be configured toreceive fuel 120 through second passage 260 and combine fuel 120 withexhaust 220. Second passage 260 formed in second body section 450 cantaper down to a narrow cross-sectional area before the walls may expandout increasing the cross-sectional area of the second passage 260forming valve seat 600. Valve seat 600 can be configured to engage valvestem 590.

The outer-peripheral face of valve stem 590 can be shaped such that inthe vicinity of the first end 540, its diameter decreases moving towardsthe outer most surface of first end 540. Valve stem 590 may end in apoint. Downstream from first end 540 can be inlet passage 610 thatextends from the outer surface of the valve stem 590 through the wall ofvalve stem 590 to piston cavity 560. Inlet passage 610 can allow fuel120 from second passage 260 that passes between valve seat 600 and valvestem 590 to flow into piston cavity 560. Fuel 120 can flow from pistoncavity 560 to second end 550 and into nozzle cavity 520. From nozzlecavity 520, fuel 120 can flow through orifice 620 into mixing chamber470. As a result of the fuel 120 flow path described above, fuel 120that passes between valve seat 600 and valve stem 590 can flow until itreaches the mixing chamber 470 where it may mix with exhaust 220 formingmixed fuel 200.

Recirculation device 110 can operate as follows. Exhaust 220 can exert apressure against piston head surface 570 creating a force 580 as shownin FIG. 2B. The direction upstream of force 580 can be generallyparallel to longitudinal axis 460.

Force 580 may cause piston 420 and valve stem 590 to slide toward secondpassage 260 and valve seat 600 upstream, generally along longitudinalaxis 460. For example, the piston 420 and valve stem 590 may slideupstream until valve stem 590 contacts valve seat 600 and the surfacesengage. This engagement may completely block all flow through secondpassage 260. Accordingly, the area of the opening between valve stem 590and valve seat 600 can be changed by actuating piston 420 and valve stem590 along longitudinal axis 460. Movement of piston 420 relative to body400 can control the flow rate of fuel 120 flowing through second passage260 and between valve seat 600 and valve stem 590.

Fuel 120 passing between valve stem 590 and valve seat 600 may flowthrough inlet passage 610 into piston cavity 560 to nozzle cavity 520.From nozzle cavity 520, fuel may flow out through orifice 620 intomixing chamber 470. In mixing chamber 470, fuel 120 may mix with exhaust220. Ultimately, fuel 120 can flow out third passage 270 as mixed fuel200 to anode compartment 140.

Fuel 120 entering second passage 260 can contact the tapered end ofvalve stem 590 as it passes through valve seat 600. As such, fuel 120can exert a pressure against the tapered surface of valve stem 590,creating a fuel force 630 as shown in FIG. 2B. Force 630 can begenerally in a downstream direction along longitudinal axis 460. The sumof force 580 and fuel force 630 may determine the position of piston 420and valve stem 590 in relation to body 400. Balancing forces 580, 630 ancontrol the flow rate of fuel 120 that flows through nozzle 410 andorifice 620 and into the mixing chamber 470.

FIG. 2B is a schematic isometric view of piston 420, according to anexemplary embodiment. FIG. 2B shows the available surface area of thepiston head 530 and valve stem 590 along with force 580 and a fuel force630 that can be applied to piston 420 and valve stem 590.

In other embodiments, fuel force 630 may be supplemented by a spring(not shown). Such a spring could be placed within piston chamber 480.For example, the spring could be configured to exert additional forceagainst piston 420 in a downstream direction. This direction could begenerally parallel to the longitudinal axis 460. Selecting the springcan set the desired anode pressure that is required to actuate thepiston. In an alternate embodiment, spring (not shown) under force oftension may be used to supplement force 580.

FIG. 3 shows an alternate embodiment of recirculation device 1010. As inFIG. 2, recirculation device 1010 may comprise a body 700 and a piston710. However, the embodiment disclosed in FIG. 3 can also have a needle720.

Similar to body 400 in FIG. 2, body 700 can receive a flow of exhaust220 in first passage 730 and fuel 120 in second passage 740. Both flowsmay mix within body 700 and be discharged as mixed fuel 200 from thirdpassage 750 as shown in FIG. 1.

Body 700 can comprise a structure with an internal cavity 760 configuredto house piston 710. For example, body 700 can comprise a first bodysection 770 and a second body section 780. Body sections 770, 780 may becoupled to each other using various mechanisms as described above.

Piston 710 can be configured to introduce a flow of fuel 120 into mixingchamber 790 similar to nozzle 410 described above. For example, piston710 can accelerate fuel 120 as it flows through piston 710. Fuel 120 canreach velocity necessary to entrain exhaust 220 with fuel 120 to permitmixing within mixing chamber 790. Piston 710 can provide passage of fuel120 from needle 720 to mixing chamber 790. Piston 710 can also controlflow of fuel 120 through second passage 740 based on exhaust 220pressure in internal cavity 760 applied against piston 710.

Piston 710 may be slideably located in internal cavity 760 formed inbody 700. Piston 710 may slide along internal cavity 760 by way of abearing or equivalent mechanism while still maintaining a sealed edge.Body 700 can be configured to limit the range piston 710 may slide ininternal cavity 760. Adequate friction between piston 710 and internalcavity 760 surface may be present to prevent rapid oscillation of thepiston 710 in response to pressure fluctuations of exhaust 220.

Piston 710 can have a first end 800 located generally upstream and asecond end 810 located generally downstream. Piston 710 can comprise apiston cavity 820 located between first end 800 and second end 810,wherein piston cavity 820 may be configured to receive needle 720 andprovide passage of fuel 130 through piston 710.

First end 800 can comprise a piston head 830 configured to receiveneedle 720. Piston head 830 can be configured to receive exhaust 220pressure at piston head surface 840. Exhaust 220 can exert a pressureagainst the piston head surface 840 creating a force 850 in a generallyupstream direction.

The outer edge of piston head 830 can be configured to seal tightagainst the inner cavity 760 surface in order to prevent exhaust 220from bypassing the piston head surface 830.

Second end 810 of piston 710 can comprise orifice 870 to allow fluidflow to pass from piston cavity 820 to mixing chamber 790. Orifice 870can be shaped to provide spray or flow distribution of fuel 120 intomixing chamber 790. A part of an inner surface of orifice 870 can bespecifically configured to receive a portion of needle 720. throughorifice 870.

Orifice 870 could be located at second end 810 most surface or locatedgenerally at second end region. Piston cavity 820 at second end 810region can decrease in diameter, narrowing while extending toward secondend 810 creating narrowing inner cavity 880. Narrowing inner cavity 880can be configured to receive needle 720 and engage needle outer surface.

Needle 720 can allow passage of fuel 120 from second passage 740 topiston 710 narrowing inner cavity 880. Needle 720 can have a first end890 located generally upstream and a second end 900 located generallydownstream. Needle 720 can have a needle central cavity 910 locatedbetween first end 890 and second end 900 providing passage from firstend 890 toward general region of second end 900. Needle 720 can extendfrom second body section 780 downstream generally parallel tolongitudinal axis 860 to the general central region of mixing chamber790.

Needle 720 first end 890 can receive fuel 120 from second passage 740and allow flow into needle central cavity 910. Needle 720 can beconfigured to slideably insert into piston cavity 820 until reachinggeneral region of narrowing inner cavity 880.

In other embodiments, needle 720 can be a separate structure which canbe coupled to first body section 770 or body 700.

Upstream of second end 900, needle 720 can have an outlet passage 920that allows passage of a fluid from needle central cavity 910 throughthe wall of needle 720 into piston cavity 820 and narrowing inner cavity880. Part of needle 720 in a vicinity of second end 900 can taper down,thereby reducing the diameter of a cross-sectional area of needle 720.The downstream most end of needle 720 may include a point. The taperedsection of needle 720 can be configured to engage with the surface ofthe narrowing inner cavity 880 and the orifice 870.

Recirculation device 1010 can operate as follows. Force 850, as shown inFIG. 3B, can be applied to piston head surface 840. This may causepiston 710 to slide generally upstream. This direction may be generallyparallel to longitudinal axis 860. Movement can cause second end 900 toprotrude from narrowing inner cavity 880 through orifice 870 as piston710 slides upstream. Piston 710 may slide upstream until second end 900of needle 720 protrudes through orifice 870. This movement can fillorifice 870, preventing or limiting further sliding and blocking flowthrough orifice 870. Accordingly, the area of the opening between piston710 narrowing inner cavity 880 and needle second end 900 can be changed.Modifying the opening area can control the flow rate of fuel 120 passingthrough orifice 870. Controlling the flow of fuel 120 through orifice870 can control the flow of fuel 120 passing through second passage 740.

A spring (not shown) can be placed within internal cavity 760 and usedto oppose force 850. For example, the spring could be configured toexert a spring force 930 against piston 830 in a downstream direction.This direction could be generally parallel to the longitudinal axis 860.The sum of force 850 and spring force 930 can determine the position ofpiston 850. The position of piston 850 can control the flow rate of fuel120 through orifice 870 into mixing chamber 790. The spring can beselected to set an anode pressure at which, piston 850 is actuated.

In other embodiments, spring force 930 can be supplemented or replacedby a hydraulic force created by pressuring the internal cavity 760upstream of piston 830.

Other embodiments of the invention will be apparent to those skilled inthe art from consideration of the specification and practice of theinvention disclosed herein. It is intended that the specification andexamples be considered as exemplary only, with a true scope and spiritof the invention being indicated by the following claims.

What is claimed is:
 1. A recirculation device, comprising: a bodydefining an internal cavity, the body comprising a first passageconfigured to receive an exhaust into the body, a second passageconfigured to receive a fuel into the body, a third passage configuredto discharge a mixture of the exhaust and the fuel from the body, and alongitudinal axis extending from the second passage to the thirdpassage; a piston slideably located within the body having a diaphragmseal fixed to an outer wall of the piston and an inner wall of theinternal cavity separating the internal cavity into a first cavitysection that is exposed to the exhaust and a second cavity sectionseparated from the exhaust, the piston comprises a piston cavityconfigured to receive a needle through the piston cavity, the pistoncavity is configured to direct the fuel towards an orifice, the orificeis located at the smallest cross-sectional area of the piston cavity,whereby the piston is actuated along the longitudinal axis of the bodytoward the second passage by an exhaust force applied to the piston bythe exhaust within the first cavity section of the body; a mixingchamber located within the body configured to receive the exhaust andconfigured to receive the fuel from the orifice; and the needle fixedlycoupled to the body comprising: a first end that receives the fuel fromthe second passage and feeds the fuel into a central cavity that extendstowards a second end; and in the general region of the second end anoutlet passage discharges the fuel from the central cavity into thepiston cavity; a spring positioned within the second cavity section ofthe body that applies a spring force on a wall of the piston thatseparates the first cavity section and the second cavity section,wherein the spring force opposes the exhaust force; wherein the positionof the piston is passively controlled by the exhaust force produced by apressure of the exhaust within the body such that the sum of the exhaustforce, the spring force, and a hydraulic force due to a pressure in thesecond cavity section determines the position of the piston and the flowrate of the fuel through the orifice into the mixing chamber.
 2. Arecirculation device according to claim 1, wherein the device isconfigured to operate within a fuel cell system.
 3. A recirculationdevice according to claim 1, wherein the fuel ejected from the orificeand the exhaust is entrained and mixed within the mixing chamber.
 4. Arecirculation device according to claim 1, wherein the exhaust isdischarged from the anode compartment of a fuel cell and fuel is ahydrogen containing fluid.
 5. A recirculation device according to claim1, wherein the exhaust inlet pressure supplied to the first passage ofrecirculation device ranges between about three to about 60 psig and thefuel pressure supplied to second passage of recirculation device rangesbetween about 30 to about 500 psig.
 6. A recirculation device accordingto claim 1, wherein at least one of the fuel and the mixture flowvelocity is configured to operate at supersonic speed.
 7. Arecirculation device according to claim 1, wherein as the needle entersthe orifice, its area is reduced until the needle fills the orifice andseals off a flow of the fuel.